1. Field of the Invention
The present invention relates to a semiconductor device suitable for a ferroelectric memory, and a manufacturing method thereof.
2. Description of the Related Art
For a semiconductor device having a ferroelectric capacitor, an annealing treatment in the oxygen atmosphere after forming a capacitor film is dispensable so that characteristics of a ferroelectric film are enhanced. Accordingly, materials not easily oxidizable are used as materials for capacitor electrodes to sandwich the ferroelectric film, or materials oxidizable but securing sufficient conductivity even after being oxidized used as the materials. Metals of the platinum family such as platinum or iridium, and oxides of platinoid elements such as IrOx are used as the materials.
Further, in order to connect the ferroelectric capacitor and other elements, an interlayer insulating film is formed in such a manner that it covers the ferroelectric capacitor; contact holes each reaching each capacitor electrode are formed through the interlayer insulating film; and a wiring contacting each capacitor electrode through each contact hole is formed above the interlayer insulating film. Aluminum is used as a material for the wiring in general, which is also used for other semiconductor devices such as a memory. The planar shape of the contact hole is a regular rectangle. The thickness of the ferroelectric film is thicker compared to films constituting other elements, and the size of the ferroelectric capacitor in the vertical direction (thickness) is relatively large. This means that the contact hole reaching to the capacitor electrode is deep.
Meanwhile, a barrier metal film such as a TiN (titanium nitride) film is formed between the capacitor electrode and the aluminum wire, as described in the Patent Document 1 (Japanese Patent No. 3045928) and the Patent Document 2 (Japanese Patent No. 3165093) shown below, since reaction occurs between aluminum and the metals of the platinum family such as platinum.
However, conventionally the coverage of the TiN film formed within the deep contact hole described above is not superior, and in some cases the film cannot prevent reaction between platinum and aluminum from occurring. Consequently, contact failure arises or large upward rising occurs, both of which may affect the upper wiring in some cases.
Prior arts are described in the Patent Document 1 (Japanese Patent No. 3045928), the Patent Document 2 (Japanese Patent No. 3165093), Patent Document 3 (Japanese Patent Application Laid-open No. Hei 4-162652), and Patent Document 4 (Japanese Patent Application Laid-open No. 2001-351920).